1. Field of the Invention
The present invention relates to a weight checking apparatus. More specifically, the present invention relates to a weight checking apparatus that calculates the weight of an item on a weighing conveyor by measuring the weight of the weighing conveyor.
2. Background Information
In a production line for food products, a weight checking apparatus for checking the weight of products and screening the products is often placed near the end of the production line. An example of a conventional weight checking apparatus is shown in FIG. 9. A weight checking apparatus 101 shown herein mainly includes a loading conveyor 102, a weighing conveyor 103, an allocating conveyor 104, a weighing portion 105, and a controller 109.
The weighing portion 105 can measure the weight of the weighing conveyor 103. Once products (hereinafter referred to as items) are conveyed to the weighing conveyor 103 from the loading conveyor 102, the controller 109 obtains weight data from the weighing portion 105 while the item is still on the weighing conveyor 103. Then, the controller 109 calculates the weight of the item. Thereafter, the controller 109 performs an allocating process at the allocating conveyor 104 to screen the item based on the calculated weight of the item. In the weight checking apparatus 101, a loading sensor 106 is provided to detect an item that has been loaded onto the weighing conveyor 103 from the loading conveyor 102, as the loading sensor 106 is utilized. The loading sensor 106 is a photoelectric sensor having a pair of projector and light receiver. As the item is loaded from the loading conveyor 102 to the weighing conveyor 103, the loading sensor 106 sends to the controller 109 a signal that indicates that an item has been detected. Then, the controller 109 obtains the weight value of the item when the item is completely loaded on the weighing conveyor 103 and the weight of the weighing portion 105 has become stable. In this manner, the weight checking apparatus 101 obtains the weight values of items sequentially, and screens the items at the allocating conveyor 104 based on their weight values.
In a production line of food products, there are various apparatuses such as a weight checking apparatus, as well as operators who monitor the apparatuses and perform manual operations. Therefore, there is a possibility that an item from outside the production line is loaded on the weight checking apparatus due to a mistake by the operator. In that case, if the item is loaded onto the loading conveyor 102, the item will be weighed at the weighing conveyor 103 and screened out at the allocating conveyor 104. However, if the item is loaded directly onto the weighing conveyor 103, since there is no signal from the loading sensor 106 to the controller 109, the weighing is not performed. Accordingly, the screening is not performed at the allocating conveyor 104. In other words, if the operator inadvertently loads an item from outside the production line onto the weighing conveyor 103, the item may pass through the allocating conveyor 104 as a normal item, and be conveyed to a subsequent process. More specifically, since a weight checking apparatus is often provided at the end of the production line, if an abnormal item passes through the weighing detection apparatus without being screened out, the problem is likely to be a serious one.
In view of the above, there exists a need for a weight checking apparatus which overcomes the above mentioned problems in the prior art. This invention addresses this need in the prior art as well as other needs, which will become apparent to those skilled in the art from this disclosure.
An object of the present invention is to prevent problems that occur when an item that is not weighed properly passes through weight checking apparatus.
A weight checking apparatus of a first aspect of the present invention includes a weighing conveyor, a loading sensor, weight detection means, weight change monitoring means, weight calculation means, and a controller. The weighing conveyor conveys an item. The loading sensor detects a loading of the item on the weighing conveyor. The weight detection means detects the weight of the weighing conveyor. The weight change monitoring means monitors a change in the weight value detected by the weight detection means. The weight calculation means calculates the weight of the item based on the weight value detected by the weight detection means. The controller switches between a weighing conveyor weight change monitoring process performed by the weight change monitoring means and an item weight calculation process performed by the weight calculation means, based on a detection signal from the loading sensor. The weighing conveyor weight change monitoring process is a control in which the weight change monitoring means monitors the change in the weight value. The item weight calculation process is a control in which the weight calculation means calculates the weight of the item.
Once an item is loaded onto the weighing conveyor of the weight checking apparatus, the loading sensor detects the loading of the item, and sends a detection signal to the controller. The controller switches between the weighing conveyor weight change monitoring process and the item weight calculation process, based on the detection signal from the loading sensor. In other words, in this apparatus, the weighing conveyor weight change monitoring process is performed until the loading of the item onto the weighing conveyor is detected by the loading sensor. When the loading sensor detects the loading of the item onto the weighing conveyor, it is possible to switch to the item weight calculation process. Then, once a period of time necessary to calculate the weight of the item elapses after switching to the item weight calculation process, it is possible to switch back to the weighing conveyor weight change monitoring process.
In this manner, it is possible to perform the weighing conveyor weight change monitoring process, in which a change in the weight value of the weighing conveyor detected by weight detection means is monitored. While the item weight calculation process is performed based on the loading of a normal item onto the weighing conveyor, however, the change is not monitored. Therefore, it is possible to detect as an error a change in the weight value of the weighing conveyor caused by something other than a normal item. For instance, if an item from outside the production line is loaded onto the weighing conveyor due to a mistake of an operator, the change in the weight value of the weighing conveyor is detected during the weighing conveyor weight change monitoring process. Accordingly, an error process such as stopping the apparatus and issuing a warning can be conducted. Weight change monitoring means and weight calculation means can be either included in the controller, or provided separately from the controller.
The weight checking apparatus of a second aspect of the present invention is the weight checking apparatus of the first aspect, further including warning means. The warning means cautions an operator by displaying a screen or issuing a warning. The controller notifies of an abnormality through the warning means when the weighing conveyor weight change monitoring process shows a change in the weight value of the weighing conveyor that exceeds a predetermined range.
When the change in the weight of the weighing conveyor exceeds the predetermined range, the warning means notifies of the abnormality. This is because the warning would be constantly issued if the normal range is not determined, since the weight value usually changes constantly due to the vibration from driving of the weighing conveyor. The weight checking apparatus of a third aspect of the present invention is the weight checking apparatus of either of the previously mentioned aspects, wherein the controller stops the weighing conveyor when the weighing conveyor weight change monitoring process shows a change in the weight value of the weighing conveyor that exceeds a predetermined range.
The weight checking apparatus of a fourth aspect of the present invention is the weight checking apparatus of any of the previously mentioned aspects, further including allocating means. The allocating means allocates the item that exits from the weighing conveyor based on the weight of the item calculated by the weight calculation means. The controller sends a predetermined command of abnormality to the allocating means when the weighing conveyor weight change monitoring process shows a change in the weight value of the weighing conveyor that exceeds the predetermined range. When the change in the weight value of the weight conveyor exceeds the predetermined range, it is likely that an item that has not been detected by the loading sensor has been loaded onto the weighing conveyor. Then, in that case, abnormal items that are not normal items tend to be conveyed from the weighing conveyor to the allocating means. Therefore, in this invention, a predetermined command for an abnormal situation is sent from the controller to the allocating means in such cases. In this way, it is possible to distinguish items that have been checked properly from items from the abnormal period. Accordingly, it is possible to perform the subsequent process efficiently. In other words, only the items from the abnormal period can be rechecked later. The predetermined command for the abnormal period is, for instance, a command to allocate the items to a separate location from where normal items are, or a command to allocate such that the items from the abnormal period are excluded from the normal production line along with items of which the weight values are not within the predetermined level.
The weight checking apparatus of a fifth aspect of the present invention is the weight checking apparatus of one of the previously mentioned aspects, wherein the controller switches the weighing conveyor weight change monitoring process to the item weight calculation process in a period between the time when the loading sensor detects the loading of the item onto the weighing conveyor and the time when the item exits the weighing conveyor. In the period between the time when the loading sensor detects the loading of an item onto the weighing conveyor and the time when the item exits the weighing conveyor (hereinafter referred to as normal item conveyance period), the normal item is loaded onto the weighing conveyor. In this period, the weight value of the weighing conveyor changes even though it is during the time period which is not for calculating the weight of the items. Therefore, in this invention, the item weight calculation process is performed instead of the weighing conveyor weight change monitoring process, at least during the normal item conveyance period. In this manner, an allocation command after the proper checking and an allocation command during the abnormal period can be clearly distinguished from each other.
These and other objects, features, aspects and advantages of the present invention will become apparent to those skilled in the art from the following detailed description, which, taken in conjunction with the annexed drawings, discloses a preferred embodiment of the present invention.